1. Field of the Invention
The present invention relates to apparatus for coating monofilaments of ceramic reinforcing materials such as silicon carbide with a predetermined thickness of matrix metal by a process of physical vapour deposition. Subsequently, the coated reinforcement may be consolidated into a metal matrix composite material having a controlled fibre spacing.
2. Discussion of Prior Art
Fibre reinforced metal matrix composites offer combinations of strength, stiffness and elevated temperature performance which are unattainable with conventional structural materials. As a result, they are currently under consideration for a wide range of applications in aerospace technology.
Typical matrix materials include titanium, aluminium or their alloys. Especially preferred are alloys of these elements which are capable of undergoing superplastic deformation.
Hitherto, the use of titanium as a matrix material has been largely confined to solid state processes undertaken at relatively low temperatures (1000.degree. C.) because of the high chemical reactivity of titanium. One well-known technique is the so-called "foil-fibre" method in which alternate layers of metal foils and ceramic fibres are hot pressed together to give a fully dense product. This process is reasonably successful for flat products, but problems sometimes arise due to incompatibility between the foil and the reinforcement. In addition, some movement of the fibres is inevitable, possibly leading to touching fibres and local inhomogeneity in the structure. A variant of the foil-fibre method uses alloy powders mixed with an organic binder and rolled into a cloth as an alternative to the metal foil. This alternative method suffers from the same risks of fibre movement but allows a greater variety of matrix materials to be used by mixing of powders.